Pick any five...

Take the first 10 natural numbers -- that's 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Pick any five of the numbers, and write them in a column, in increasing order. Then take the five remaining numbers -- the ones you didn't pick -- and write them in a second column, in decreasing order.

In each row, subtract the smaller number from the larger one, giving you a third column. (See the example below.) Now add the numbers in the third column.

Re: Pick any five...

Maths: It is still amazing to me how something that starts so simply (one pebble plus another pebble makes two pebbles) can become so rich and varied so quickly.

I mean, you can make a circle by standing on one foot and dragging the other one around on the sand. Who could possibly think that comparing the distance your feet are apart to the length your foot travels would be a number that has digits going on forever ...

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman